U.S. patent application number 11/578487 was filed with the patent office on 2007-11-01 for method and system for transmission of information.
This patent application is currently assigned to Kongsberg Automotive AB. Invention is credited to Tommy Fristedt.
Application Number | 20070253478 11/578487 |
Document ID | / |
Family ID | 38648290 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070253478 |
Kind Code |
A1 |
Fristedt; Tommy |
November 1, 2007 |
Method and System for Transmission of Information
Abstract
The present invention relates to a method for serial
transmission of information between at least one transmitter (7, 9,
14, 15) and at least one receiver (7, 9, 14, 15), with the said
information being transferred by means of voltage pulses (13). The
invention comprises the following steps: making an association
between the information that is to be transferred and the time (T)
between two predetermined edge levels (U1, U2) of a voltage pulse;
generation of a voltage pulse in the transmitter with a time
difference between the flank levels (U1, U2) corresponding: to the
information that is to be transferred; and transmission of the
voltage pulse from the said transmitter to the said receiver. The
invention also relates to a system for such transmission of
information.
Inventors: |
Fristedt; Tommy; (Bottnaryd,
SE) |
Correspondence
Address: |
EDWARDS ANGELL PALMER & DODGE LLP
P.O. BOX 55874
BOSTON
MA
02205
US
|
Assignee: |
Kongsberg Automotive AB
Box 504
Mullsjo
SE
S-565 28
|
Family ID: |
38648290 |
Appl. No.: |
11/578487 |
Filed: |
April 15, 2005 |
PCT Filed: |
April 15, 2005 |
PCT NO: |
PCT/SE05/00544 |
371 Date: |
October 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60521597 |
Jun 2, 2004 |
|
|
|
Current U.S.
Class: |
375/239 |
Current CPC
Class: |
H04B 2203/547 20130101;
H04B 3/548 20130101 |
Class at
Publication: |
375/239 |
International
Class: |
H03K 7/04 20060101
H03K007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2004 |
SE |
0400978-3 |
Claims
1. Method for the serial transmission of information between at
least one transmitter (7, 9, 14, 15) and at least one receiver (7,
9, 14, 15), with the said information being transferred by means of
voltage pulses (13), characterized in that it comprises the steps:
making an association between the information that is to be
transferred and the time (T) between two predetermined edge levels
(U.sub.1, U.sub.2) of a voltage pulse; generation of a voltage
pulse in the transmitter with a time difference between the flank
levels (U.sub.1, U.sub.2) corresponding to the information that is
to be transferred; and transmission of the voltage pulse from the
said transmitter to the said receiver.
2. Method according to claim 1, characterized in that the time (T)
between two predetermined flank levels (U.sub.1, U.sub.2) of a
voltage pulse (23) is variable.
3. Method according to claim 1 or 2, characterized in that the time
(T) between the two predetermined flank levels (U.sub.1, U.sub.2)
of the voltage pulse (23) varies in predetermined steps
(T.sub.p).
4. Method according to any one of the preceding claims,
characterized in that it comprises transmission of information to
two or more receivers with one receiver being addressed at a
time.
5. Method according to claim 4, characterized in that the
communication between transmitter (7, 9, 14, 15) and receiver (7,
9, 14, 15) comprises changing the address of the receiver (7, 9,
14, 15).
6. Method according to any one of the preceding claims,
characterized in that it is arranged to control an electric motor
(18).
7. Method according to claim 6, characterized in that it is
utilized to control an electric motor (18) which consists of a fan
motor arranged for ventilation of vehicle seats (1).
8. System comprising a control unit (9) and at least one fan unit
(7, 14, 15), which fan unit (7, 14, 15) is arranged for ventilation
of vehicle seats, in which the control unit (9) and the fan unit
(7, 14, 15) are arranged to communicate with each other by means of
voltage pulses (23) via a serial communication bus (10),
characterized in that the time (T) between two predetermined flank
levels (U.sub.1, U.sub.2) of a voltage pulse (23) is variable.
9. System according to claim 8, characterized in that the time (T)
between the two predetermined flank levels (U.sub.1, U.sub.2) of
the voltage pulse (23) is the information carrier of the
communication protocol.
10. System according to claim 8 or 9, characterized in that the
time (T) between the two predetermined flank levels (U.sub.1,
U.sub.2) of the voltage pulse (23) varies in predetermined steps
(T.sub.p).
11. System according to any one of claims 8-10, characterized in
that when there are several receivers, one receiver can be
addressed at a time.
12. System according to claim 11, characterized in that the
communication between transmitter (7, 9, 14, 15) and receiver (7,
9, 14, 15) comprises changing the address of the receiver (7, 9,
14, 15)
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for serial
transmission of information between at least one transmitter and at
least one receiver, with the said information being transferred by
means of voltage pulses.
[0002] The invention also relates to a system comprising a control
unit and at least one fan unit, which fan unit is arranged for
ventilation of vehicle seats, with the control unit and the fan
unit being arranged to communicate with each other by means of
voltage pulses via a serial communication bus.
BACKGROUND ART
[0003] There is currently a need to communicate to and from an
electric motor, that is to transmit, for example, control commands
to a microcomputer located in the motor that is in contact with the
motor and obtains, for example, error messages from this
microcomputer. This applies, for example, to fan motors arranged in
vehicles, more specifically fan motors arranged in ventilated seats
in vehicles, in accordance with what is described below.
[0004] For reasons of comfort and safety, ventilated seats are
currently used in vehicles. For this purpose, both the driver's
seat and other vehicle seats can be provided with ventilation ducts
that lead from a fan located in the vicinity of the seat to one or
more openings in the seat. Such openings are normally located in
the seat cushion, but can also be located in the back support. The
fan can be arranged so that it either forces or extracts air. In
this way, ventilation of the surface of the vehicle seat in
question is made possible, which in turn provides an increased
sensation of comfort for the, driver or passenger in the respective
vehicle seat.
[0005] Patent DE10009128 C1 shows a fan for ventilation of vehicle
seats, in which a control unit integrated in the fan unit, is
supplied with control signals from an external control unit. The
control unit integrated in the fan unit supplies, in turn, the fan
motor with drive voltage on the basis of the control information
received. This drive voltage for the fan motor reaches the control
unit integrated in the fan unit via a separate supply lead for
drive voltage.
[0006] A disadvantage of previously known technology for direct
current motors, is that a lot of cabling is required in order to
achieve both the transmission of signals and the transmission of
power. There are also difficulties associated with the transmission
of control signals, as digital information is transferred in the
form of pulse trains where the pulses represent ones and zeros, and
where a large number of pulse edges can cause both electromagnetic
interference and mechanical interference to the controlled motor.
In particular, there is a need to provide a communication protocol
that gives an efficient and reliable transmission of information
between, for example, a central control unit and one or more
controlled units.
DISCLOSURE OF INVENTION
[0007] An object of the present invention is to provide an improved
method and improved system for the transmission of information, for
example in association with controlling a motor driven by direct
current, by means of which the problems stated above can be
solved.
[0008] This object is achieved by means of a method of the type
mentioned in the introduction, which is characterized in that it
comprises, in addition, the following steps: making an association
between the information that is to be transferred and the time
between two predetermined edge levels of a voltage pulse;
generation of a voltage pulse in the transmitter with a time
difference between the flank levels corresponding to the
information that is to be transferred; and transmission of the
voltage pulse from the said transmitter to the said receiver.
[0009] The object is also achieved by means of a system of the type
mentioned in the introduction, which is characterized in that the
time between two predetermined flank levels of a voltage pulse is
variable.
[0010] By means of the invention, a method and a system are
provided that give an efficient protocol for the transmission of
information. In particular, the invention provides a rational and
highly efficient system as far as cost is concerned, which still
provides maximum performance, that is on a level with that provided
by other more expensive systems.
[0011] In addition, the invention contributes to a reduction in
problems relating to EMC (electromagnetic compatibility) by
rationalizing and minimizing the number of pulses that are used for
the said transmission of information.
BRIEF DESCRIPTION OF DRAWINGS:
[0012] The invention will be described in detail in the following
with reference to the attached drawings. These drawings are used
only for the purpose of illustration, and are not to be regarded as
limiting the present invention.
[0013] FIG. 1 shows a perspective view of a vehicle seat with which
the present invention can be used;
[0014] FIG. 2 shows a diagram of a fan network;
[0015] FIG. 3 shows a diagram of a fan unit;
[0016] FIG. 4 shows an example of a communication pulse according
to the invention;
[0017] FIG. 5 shows an example of a communication pulse according
to the invention; and
[0018] FIG. 6 shows an example of a communication pulse train
according to the invention.
MODE(S) FOR CARRYING OUT THE INVENTION
[0019] The following description exemplifies the present invention
when it is used for a fan motor arranged for ventilation of a
vehicle seat with reference first to FIG. 1. This area of
application is, however, not to be regarded as limiting the
invention, which can be used for several different kinds of serial
data communication.
[0020] For increased comfort, the seat cushion 2 and back support 3
of a vehicle seat 1 can be provided with ventilation and
temperature control of the surfaces or areas on which a driver or
passenger in the vehicle is expected to sit. The seat cushion 2
will be described in the following, but of course the corresponding
considerations apply for the back support 3. In a vehicle, both the
driver's seat and the other seats can be equipped with ventilation
by forcing or extraction of air. The forced or extracted air is
distributed via at least one opening 4 that is arranged in the seat
cushion 2. In the case of forcing of air, this supplied air is
taken through a duct 5 in the seat cushion 2 and out towards the
person who is sitting on the seat in question, via the distributing
opening 4. In the case of extraction of air, this extracted air is
taken from the person who is sitting in the seat in question
through the duct 5 in the seat cushion 2 via the distributing
opening 4.
[0021] Forcing or extracting of air is preferably carried out by
means of a fan 6 driven by a direct-current motor in a fan unit 7.
In FIG. 1, the actual motor for the fan 6 is not shown. By
regulating the speed of the fan 6, a particular amount of air can
be taken to or from the seat cushion 2. In this way, an accurately
adjusted temperature can be obtained on the surface of the seat if
a temperature sensor 8 arranged in the seat is arranged to
communicate with a control unit 9 for controlling the fan 6 via a
link 10, which control unit 9 is external in relation to the fan
unit 7. The fact that the control unit 9 is external means that it
is not arranged in the same physical casing or the like as the
actual fan unit 7, but consists of a central control unit for the
temperature control and ventilation of the seat 1 and is used for
operation of the fan motor 8.
[0022] The control of the speed of the fan 8 is carried out, for
example, by a supply of the PWM type (Pulse Width Modulation). By
means of this, the fan is supplied with a pulse train generated in
the first control unit 9, which means that during the pulse train's
positive with-voltage phases, the fan 7 is with voltage, while
during the pulse train's without-voltage phases, it is without
voltage. Thus, during a supply period of the Pulse Width Modulated
supply, the fan 7 obtains drive voltage from and including the
rising edge up to and including the falling edge. The supply can be
carried out with a frequency that lies within the range approx. 20
Hz-200 kHZ, that is within a wide frequency range. It should,
however, be noted that the invention is not limited to the supply
having to be carried out at any particular frequency or within any
particular frequency range. Other supply signals are also possible
within the framework of the present invention, for example via any
type of known voltage regulator.
[0023] FIG. 2 shows schematically a fan network 11 in which the
present invention is used. The control unit 9 consists of a
"master" unit comprising a first microcontroller 12 and a drive
unit 13 arranged to drive two fan units 14, 15 which correspond to
the fan unit with the reference numeral 7 in FIG. 1. The drive unit
13 is connected to a drive voltage U. These fan units 14, 15
constitute "slave" units. The control unit 9 is connected to the
fan units 14, 15 via the said link 10 that consists of a fan
network bus. All the units are connected to a common earth
potential 16.
[0024] A fan unit 14 will now be described in greater detail with
reference to FIG. 3. The fan unit 14 is essentially the same design
as the fan unit 15 (cf. FIG. 1). The fan unit 14 comprises a second
microcontroller 17 and a fan motor 18 which are connected to the
link 10 which defines a fan network bus. After the input 19 to the
fan unit 14, the input signal is divided so that it goes both to
the fan motor 18 and to the second microcontroller 17 comprised in
the fan unit 14. At the supply input 20 of the fan motor 18, there
is a diode 21 and stabilizing capacitor 22 that are intended to
maintain the supply voltage to the fan motor 18, irrespective of
the condition of the supply at the time. The diode 21 and the
capacitor 22 also remove electrical interference that can prevent
the second control unit 17 from reading information transmitted via
the fan network bus 10.
[0025] The first microcontroller 12 is connected to the drive unit
13 and arranged to communicate with the drive unit 13 in order to
be able to control this. By switching off the drive unit 13 for a
certain period of time in order to achieve a voltage drop-out
during this time, the first control unit 9 can communicate with the
fan units by creating a negative pulse in this way. The
communication is received by the second control unit 17 arranged in
the respective fan unit 14, 15. The communication can also be
carried out from the respective fan unit 14, 15 to the control unit
9 via the fan network bus 10. This communication will be described
in greater detail below.
[0026] The nominal high level of the output signal of the drive
unit 13 is thus at the same level as the supply voltage of the fan
motor 18. When the output signal of the drive unit 13 has a low
level, it corresponds approximately to the earth level in the
system, being at least less than a predetermined limit value. By
this means, as mentioned above, the said capacitor 22 maintains the
supply voltage so that the fan motor 18 essentially receives a
direct current supply.
[0027] An object of the present invention is to minimize the number
of pulses for the transmission of information between the control
unit 9 and the fan units 14, 15. How this is carried out is
described below, with reference also to FIG. 4. By letting the time
T for a negative pulse 23 be variable between a number of
predetermined periods of time T, where each period of time T
corresponds to a digital word, a digital word can be transmitted by
only sending one pulse 23 and measuring the time between the limit
values U.sub.1 and U.sub.2 of the edges 24, 25 of the pulse 23. The
limit values U.sub.1 and U.sub.2 can be the same, or there can be a
hysteresis .DELTA.U. The length of the digital word is dependent
upon how many unique periods of time T are defined in the system.
Several consecutive negative pulses 23 at short intervals can
define a longer digital word.
[0028] With reference now also to FIG. 5, each negative pulse 23
that is sent from the control unit 9 to the relevant fan unit 14,15
is preferably constructed of a number of basic pulses 26, where the
duration T.sub.p of a basic pulse is, for example 256 .mu.s. A
command can then be constructed of one, two or more consecutive
basic pulses 26 in order to constitute a negative pulse of a
certain duration depending upon what is to be communicated. The
reading off by the second microcontroller 17 has been programmed
with a tolerance range for interpreting the received pulse 23.
[0029] The limiting factor here is that the voltage drop-out must
be of such a short duration that the relative effect on the fan
motor 18 is small. The capacitor 22 in the fan unit 14, 15 has, as
mentioned above, the function of stabilizing the drive voltage of
the respective fan motor 18, for which reason the performance of
the capacitor 22 is of significance for how long the periods with
voltage drop-out (that is the negative pulses 23) can be. In
addition, the resolution is also limiting, that is how small the
time differences can be so that it is still possible to distinguish
between the different unique periods of time for the negative
pulses with an adequate margin of error.
[0030] By defining a number of unique periods of time T, consisting
of a unique number of basic pulses 26, for the negative pulses,
where each period of time T is allocated a special significance, a
protocol for communication between control unit and fan units can
be established. Such a protocol must be able, among other things,
to handle addressing of the respective fan units. In the present
example, there are two fan units 14, 15, each of which has a
network address, which allows the control unit 9 to communicate
with one fan unit 14, 15 at a time. The address is not allocated
until after the unit 14, 15 in question has been mounted in the
intended place, for which reason it does not initially have any
address at all, but is allocated an address later, which address is
stored in the second microcontroller 17, or, where such exists, in
a separate memory in the fan unit 14, 15 (not shown). The address
can then be changed if the need arises, for example, for
service.
[0031] The respective fan unit 14, 15 is also arranged to
communicate with the control unit 9 by creation of load pulses.
These load pulses are communicated via the fan network bus 10 to
the control unit 9. The load pulses are created by the second
microcontroller 17 in the respective fan unit 14, 15 switching on
the windings of the motor 18 in question via a link 27 between the
second microcontroller 17 and the fan motor 18. The load pulses are
then created by short commutations in order to create current
pulses that can be detected in the corresponding control unit. This
corresponds to the motor 18 consuming more current. This increase
in current on the fan network bus 10 constitutes the said load
pulses, which are detected by the drive unit 13 of the control unit
9. Communication from the respective fan unit 14, 15 to the control
unit 9 is normally carried out only after an enquiry from the
control unit 9, see the command examples below. On account of the
commutation of the motor 18, communication from the respective fan
unit 14, 15 to the control unit 9 can only take place when the fan
motor 18 concerned is stationary. The commutation brings about
current changes in the fan network bus 10, which are difficult to
distinguish from load pulses. Thus, for example, error reports can
not be sent to the control unit 9 from the fan unit in question 14,
15 as long as the fan motor 18 in question is activated. In such a
case, error data is stored in a memory in the second
microcontroller 17, or if such exists in a separate memory in the
fan unit (not shown), and is sent as error status to the control
unit 9 when the fan motor 18 in question stops.
[0032] Examples of commands from the control unit 9 to the fan unit
14, 15 without requiring a response from the fan unit 14, 15 are:
[0033] Change fan speed [0034] Start fan [0035] Stop fan [0036]
Change fan unit's address [0037] Resetting of error status
[0038] Examples of commands from the control unit 9 to the fan unit
14, 15 where a response is required from the fan unit 14, 15 are:
[0039] Reading off of error status [0040] Reading off of
distinguishing data
[0041] Reading off of so-called distinguishing data is only
required when two "slave" units 14, 15 have been given the same
address and must be distinguished in some other way. For example, a
unique serial number can be stored in the second microcomputer 17
during manufacture of the fan unit 14, 15. Another possibility is
for a unique random number to be generated in the second
microcontroller 17 when reading off of distinguishing data is
requested.
[0042] An example of a communication protocol with the
functionality described above is shown below. Here the pulses
correspond to two information bits, but these are combined in pairs
in order to form digital words of four bits. This does not apply to
"Start" and "Stop" which are in addition to the list below.
TABLE-US-00001 Information transmitted Number of basic pulses of
256 .mu.s Binary number 00 8 Binary number 01 24 Binary number 10
40 Binary number 11 56 Start 72 Stop 88 Transmission pause
>104
[0043] The meaning of the different digital words can be written in
a separate table: TABLE-US-00002 Digital word Meaning 0000 Speed of
fan motor 0001 Speed of fan motor 0010 Speed of fan motor 0011
Speed of fan motor 0100 Speed of fan motor 0101 Speed of fan motor
0110 Speed of fan motor 0111 Speed of fan motor 1000 Change address
of "slave" 1001 Reset error status 1010 Read error status 1011 Read
distinguishing data 1100 Not used 1101 Not used 1110 Not used 1111
Not used
[0044] An example of a communicated sequence from the control unit
9 to a fan unit 14, 15 is shown in FIG. 6. The pulse 28 is a start
pulse consisting of 72 basic pulses, the pulses 29, 30 thereafter
give the address of the required "slave" unit. The pulses 31, 32
consisting of 24 and 40 basic pulses respectively, send the digital
word 0110, which is a specific fan speed. The pulses 33, 34 each
consisting of 40 basic pulses, send the digital word 1010, which
means that the error status is to be read off. The pulse 35 is a
stop pulse consisting of 88 basic pulses, which means that this
transmission to the "slave" in question is over. The pulse
distances 36 exceed 104 basic pulses, for which reason these
delimit each word that is transmitted.
[0045] The invention is not limited to the embodiments described
above, but can be varied freely within the framework of the
following patent claims. For example, it can be utilized freely for
all kinds of serial communication between a transmitter and a
receiver, in particular where there is a need to reduce the number
of pulses transmitted.
* * * * *